>Given the angle of the roof though, I can't help imagining that >Korra's about to roll forwards and keep rolling until she goes off the >edge. Maybe it just looks steeper than it really is.

It isn't quite as steep as it looks, and although it's hard to tell from this angle, the roof is also slightly concave (it ramps upward a little at the edge). Also, that might be part of the reason why Corwin's left arm is where it is. :)